Standards for the WLAN technology have been developed as Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards. IEEE 802.11a and b use an unlicensed band at 2.4 GHz or 5 GHz. IEEE 802.11b provides a transmission rate of 11 Mbps and IEEE 802.11a provides a transmission rate of 54 Mbps. IEEE 802.11g provides a transmission rate of 54 Mbps by applying Orthogonal Frequency Division Multiplexing (OFDM) at 2.4 GHz. IEEE 802.11n provides a transmission rate of 300 Mbps for four spatial streams by applying Multiple Input Multiple Output (MIMO)-OFDM. IEEE 802.11n supports a channel bandwidth of up to 40 MHz and, in this case, provides a transmission rate of 600 Mbps.
Since the above-described standards for the WLAN technology maximally use bandwidth of 160 MHz and support eight spatial streams, IEEE 802.11ax standardization is being discussed in addition to IEEE 802.11ac standard maximally supporting a rate of 1 Gbit/s.
In the WLAN standardization process, a method of, at a non-AP station (STA), receiving a signal from an access point (AP) STA using a multi-user beamforming method was introduced in IEEE 802.11ac. However, technology of applying multi-user scheduling to transmission from a non-AP STA to an AP in addition to data transmitted to the non-AP STA has been required.